Rapid kinetics techniques have become a standard approach for investigating both chemical and biochemical reaction mechanisms. Such techniques include perturbation relaxation kinetics such as temperature-jump (T-jump), stopped-flow kinetics, and flash photolysis. The mixture of products and reactants is usually analyzed using optical methods, for example by monitoring absorption changes at one or more wavelengths. This is a proposal to purchase a single instrument which will go well beyond the capabilities of any instrumentation on this Campus and which will provide for the needs of a considerable number of chemists, biochemists, and biophysicists. We are proposing to purchase an apparatus of modular design in which reactions can be analyzed by using a rapid scanning spectrophotometer. Reactions can be initiated either by a light flash (flash photolysis) or by rapid mixing of reagents (stopped-flow). The Union Giken instrument also has accessories for studying reactions by temperature- or pressure-jump, and for monitoring reactions by fluorescence emission. This remarkably versatile instrumentation package will make possible many experiments which cannot now be performed on this campus. In general, such instrumentation is largely unavailable in this country and can be considered as state-of-the-art technology. An instrument of comparable capability may be available from Update, Inc. and this will be considered as a viable alternative. It should be noted that the ability to monitor changes over a wide spectral range (100 nm) is required for analyzing mixtures with multiple components where the absorption spectra of the components overlap. In these cases there are no isosbestic points, so dual wavelength capability is insufficient. Present instruments for rapid kinetics studies on campus are very limited in comparison to the proposed instrumentation. For the most part these instruments are designed for specific experimental systems and are not easily adapted or available for wider use. No facility exists on campus for the use of a rapid scanning spectrophotometer for kinetics analysis of fast reactions. We wish to emphasize that the instrumentation package whose purchase we are proposing is designed to appeal to many investigations in a wide range of research areas. The availability of such an apparatus would stimulate work which would otherwise not be feasible.